Now, I've never had this problem before, so I ask you to please help me. After normally turning on my PC, I get welcomed with a message
Your current network has a .local domain, which is not recommended and incompatible with the Avahi network service discovery. The service has been disabled.
A problem has occurred at the same time with Wi-Fi and wired connection, and so I can no longer connect to the Internet.
I went browsing the forum. In this post I scavenged
sudo -i gedit /etc/default/avahi-daemon
but the problem hasn't gone away. Could someone please help me?